Microorganisms are involved in the manufacture of food and feed products including most dairy products. Thus, bacterial cultures, in particular cultures of bacteria that are generally classified as lactic acid bacteria are essential in the making of all fermented milk products, cheese and butter. Cultures of such bacteria may be referred to as starter cultures and they impart specific features to various dairy products by performing a number of functions.
Commercial dairy starter cultures are generally composed of lactic acid and citric acid fermenting lactic acid bacteria. In the present context, the expression “lactic acid bacteria” designates a group of Gram positive, catalase negative, non-motile, microaerophilic or anaerobic bacteria which ferment sugar with the production of acids including lactic acid as the predominantly produced acid, acetic acid, formic acid and propionic acid. The industrially most useful lactic acid bacteria are found among Lactococcus species, Streptococcus species, Enterococcus species, Lactobacillus species, Leuconostoc species and Pediococcus species.
Commonly used dairy starter culture strains of lactic acid bacteria are generally divided into mesophilic organisms having optimum growth temperatures at about 30° C. and thermophilic organisms having optimum growth temperatures in the range of about 40 to about 45° C. Typical organisms belonging to the mesophilic group include Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Leuconostoc mesenteroides subsp. cremoris, Pediococcus pentosaceus, Lactococcus lactis subsp. lactis biovar. diacetylactis and Lactobacillus casei subsp. casei. Thermophilic lactic acid bacterial species include as examples Streptococcus thermophilus, Enterococcus faecium, Lactobacillus lactis, Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus acidophilus. 
The dairy starter cultures are also classified according to their specific species composition and preferred industrial use. A pure starter culture comprises only a single specie and a mixed culture comprises two or more different species. Commercial relevant mesophilic mixed cultures include:                “O-culture” comprising Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris.         “D-culture” comprising Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis biovar. diacetylactis.         “L-culture” comprising Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris and Leuconostoc mesenteroides subsp. cremoris.         “LD-culture” comprising Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis biovar. diacetylactis and Leuconostoc mesenteroides subsp. cremoris.         
An O-culture is used to make cheese without holes (Cheddar, Cheshire, Feta). A D-culture is used to make butter. A L-culture is used to cheese with only small holes (cottage cheese) and curdled milk products with low CO2-production. A LD-culture is used to make cheese with normal hole sizes, curdled milk products (junket) and sour butter. Commercially, a LD-culture is currently one of the most used mixed cultures.
Commercial relevant thermophilic mixed cultures include:                “Yoghurt culture” comprising Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.         “Thermophil cheese culture” comprising Streptococcus thermophilus and Lactobacillus helveticus.         
An Yoghurt culture is used to make yoghurt and special Italian cheeses. An Thermophil cheese culture is used to make emmentaler cheese and special Italian cheeses.
Commercial starter cultures may commonly be distributed as frozen cultures. Highly concentrated frozen cultures are commercially very interesting since such cultures can be inoculated directly into milk without intermediate transfer. In others words, such highly concentrated frozen cultures comprises so many bacteria that dairies do not have to make in-house bulk starters. A “bulk starter” is defined herein as a starter culture propagated at the dairy plant for inoculation into milk. Highly concentrated cultures may be referred to as direct vat set (DVS)-cultures.
In order to comprise sufficient bacteria a commercial relevant highly concentrated frozen culture generally has a weight of at least 50 g and a content of viable bacteria of at least 109 colony forming units (CFU) per g.
Another presentation of commercial highly concentrated DVS-starter cultures is as freeze-dried or lyophilized cultures in the form of a powder. In this form, the starter can be shipped without refrigeration.
The article of F. J. Chavarri et al (Biotechnology letters, vol 10, 1, 11-16 (1988), “Cryoprotective agents for frozen concentrated starters from non-bitter Streptococcus Lactis strains”) describes that the storage viability of a frozen pure Streptococcus lactis culture could be improved by addition of 5% lactose or 5% sucrose. The lactose or sucrose worked as cryoprotective agents. Streptococcus lactis is a former name of Lactococcus lactis subsp. lactis. 
Similarly, the article of R. Cárcoba et al (Eur Food Res Technol (2000) 211, 433-437, “Influence of cryoprotectants on the viability and acidifying activity of frozen and freeze-dried cells of the novel starter strain Lactococcus lactis subsp. lactis CECT 5180”) describes that the storage viability of a frozen pure Lactococcus lactis subsp. lactis culture could be improved by addition of different cryoprotective agents such as sugars (lactose, sucrose and trehalose), glutamic acid and gelatin.
The present inventors are not aware of any commercial available highly concentrated frozen cultures that comprise significant amounts of cryoprotective agents.
EP259739 describes different suitable cryoprotective agents for freeze-dried cultures. A freeze-dried culture in the form of a powder is physically significant different from a frozen culture among others due to that a freeze-dried powder comprises significant less water as compared to a frozen culture. Accordingly, it is submitted that the skilled person would prima facie not consider that a specific cryoprotective agent described as useful for a freeze-dried culture would also be similar useful in a frozen culture.
WO00/39281 (Chr. Hansen A/S) describes a liquid starter culture stabilized by different cryoprotective agents. Page 5, lines 5-7 reads “the expression “liquid starter culture” relates to non-frozen liquid starter cultures having a liquid phase, e. g. an aqueous phase, content that is typically in the range of 50-90% by weight”. Consequently, the liquid culture described in WO00/39281 is a non-frozen culture.